Volume 54, Nº 1 (2018)

Ground displacement reconstruction is an ill-posed problem. Therefore, additional assumptions that ensure the stability of the resulting solution have been used to solve it. Interactive correction of the trend in the time domain, which makes it possible to remove a group of long-period trends from the seismic record without repeating the procedure, can be used as an alternative to the regularization of the solution in the deconvolution algorithm. Interactive trend correction is used within the proposed criterion. In the paper, the algorithm for calculating accelerograms from velocigrams with an integrated procedure for the interactive correction of the long-period trend has been given. The efficiency of the algorithm, which is based on the relationship of the differential equation of motion of the velocimeter pendulum to the true acceleration of the foundation bed, has been shown experimentally.

The possibility of registering high-frequency seismic noise in a broadband frequency range (f = 5–400 Hz) has been considered. The use of an accelerometer on based on the S mode of bending vibrations increases the sensitivity and expanses the frequency range. The operating principle of the accelerometer and its main technical characteristics have been described. Pilot registration of seismic noise was organized at Nachiki seismic station in Kamchatka. The comparative results of tidal effects in seismic noise have been presented according to the data of the broadband accelerometer (f = 5–400 Hz) and resonance sensor (f₀ = 30 Hz) during long-term registration on a common base.

The implications of a broad range of factors for the intensity of the oceanic gravimetric effect has been estimated. These factors include dissipation, mass correction, the selection of the oceanic tidal model and Earth’s density model, and discarding the near-zone approximation, as well as allowance for the ellipticity of the Earth and the relative, Coriolis, and inertial accelerations. It has been shown that, with the presentday requirements to computational accuracy, the joint effect of these factors, rather than the separate contributions of each individual factor are of primary importance. The load Love numbers are calculated up to degree n = 50000.

Earthquakes, which result from tectonic movements within the bowels of the Earth, reflect spatiotemporal changes in the stress field of the geologic medium. Weak regional earthquakes indicate the activation of some elements of seismotectonic zones and preparation of strong earthquakes. The travel times of Pand S-waves and V_P/V_S ratios are also a source of information on the regional tectonic setting; sometimes this information helps to reveal blind faults. The paper analyzes local earthquakes in a seismically active region, which comprises the Greater Caucasus, the Kura Depression, Transcaucasia, and the western Caspian Region. Based on a large database of hypocenter parameters, P- and S-wave travel times, and areal V_P/V_S ratio distributions, we identified seismotectonic zones with characteristic anomalous features and outlined gradient zones where V_P/V_S anomalies reverse sign. It is found that the V_P/V_S ratio field complies with the regional stress field and deep seismotectonic setting. Zones where anomalies reverse sign (gradient zones) are most likely confined to blind faults. Areas of the high gradient of the field can be put down to blind tectonic structures (faults) or the incipient sources of future strong earthquakes. V_P/V_S ratio monitoring and mapping will make it possible to identify the source zones of forthcoming earthquakes.

The Armenian seismic system, which has a threshold magnitude of 6.2, has been identified based on the method of seismic entropy, makes it possible to monitor nucleation of strong earthquakes in the magnitude range of 6.2 ≤ M < 6.6, as well as to assess the seismic situation in Armenia and neighboring countries. A study of energy and track diagrams has revealed a fan-shaped tectonic pattern of stress concentrations with an apex in the Kurdistan knot. The analysis of entropy accumulation in seismic cycles carried out for the hierarchy of seismic systems of the Armenian Highlands helped in the identification of prognostic criteria. The results have been compared to the dynamics of Akhurian reservoir filling in 1983–2016.